During the past century, internal combustion engines have proliferated. Their general replacement of external combustion engines can be attributed to advantages they offer in efficiency, power-to-size ratio, versatility, and the like. The use of connecting rod and crankshaft, with camshaft control to deliver power from reciprocating pistons has been eminently successful as attested by widespread use. However this arrangement which has been so successful in its time imposes certain limitations (particularly on the efficiency and pollution control of engines) which are very difficult to overcome. On the other hand the enormous expansion of technical civilization throughout the world has alerted mankind to the need for conservation of non-renewable resources and to the dire need for pollution control.
To accommodate these sociological requirements by reducing the limitations of present day engines requires a "quantum leap" in engine design such as occurred in the transition from external to internal combustion engines.
The present invention provides the basis for the design changes required to optimize the operating characteristics and manufacturing conditions of engines using presently available technology and materials and permits additional improvements as more advanced materials and technology become available.
Optimization of efficiency and minimization of pollution associated with combustion and thermodynamic processes which occur in the combustion chamber portion of the cylinder requires control of piston motion, of valve motion, of fuel injection, of ignition and the like to a degree which mechanical systems have not been able to provide in a practical manner.
Many inventors have recognized these problems and offered partial and piecemeal solutions. A particularly interesting solution is proposed by G. F. Chatfield in U.S. Pat. No. 4,459,945 where a good discussion of limitations of the rod-crankshaft-camshaft arrangement is presented (see also references therein). That discussion deals with "timing loses", "heat losses" and "volumetric efficiency" as a function of engine speed. Chatfield's invention replaces the rod-crankshaft mechanism by special cams and yokes to obtain better control of piston velocity within the cylinder For different applications and conditions, cams of different shape are required and each special cam provides only limited control of piston motion. Moreover his invention does not address the question of improved control of ignition, fuel injection, valve motion, and the like.
The limits to efficiency due to the "angular and moment arm changes that the conventional connecting rod undergoes in its relationship with the power output shaft and power piston" have been discussed by R. L. Giulianna et al. in U.S. Pat. No. 4,498,430 (and references cited therein). Their invention provides a partial solution to this problem (impedance matching between power source and load as a function of time) using a very complicated mechanical device which, of course, introduces additional frictional losses, and also impacts unfavorably on manufacturing cost and reliability.
Both of the aforementioned patents also promise improved pollution control through longer piston stroke. It is well known that a longer stroke allows the remaining fuel to burn at a lower temperature near the end of the stroke.
At lower temperatures, chemical equilibrium is shifted to the region where combustion is more complete and a smaller fraction of harmful pollutants are emitted. However the reduction of carbon dioxide emission can only be achieved by improving efficiency and with the use of fuels such as natural gas (methane) which burns with the production of less carbon dioxide per B.T.U. than gasoline. A long stroke also permits a lower exhaust temperature increasing the thermodynamic limit to maximum efficiency. It is evident that optimum pollution control can only be obtained by exact control of all pertinent engine parameters.
Attempts to improve efficiency by "adjustment of the compression ratio" (automatically or otherwise) are described by J. W. Akkerman in Canadian Patent No. 1,180,963 and references therein. That invention also requires a complicated mechanical mechanism which deals with the problem of providing an optimum pressure in the firing chamber at the instant of firing.
The problems of efficiency and pollution control have been addressed by numerous other inventors. S. Konther et al in U.S. Pat. No. 4,408,578 describe a complicated mechanism to change linear motion to rotational motion. A. J. Crocker in U.S. Pat. No. 4,381,740 provides greater time for the power portion of engine cycle, than for the exhaust portion of the engine cycle through the use of complicated linkages.
All previous inventions have approached the problems of engine design in a piecemeal fashion and have not provided sufficient control to achieve optimal operating conditions. Moreover the partial solution of one problem generally exacerbates other problems, for example a complicated mechanical mechanism is introduced and its use reduced the reliability of the engine and increases its manufacturing cost or pollution control is achieved using a catalytic converter which reduced the efficiency of the engine thereby producing a larger quantity of carbon dioxide exhaust for a given energy output.
It has also been widely recognized that, for automotive purposes, electric powered cars offer high energy conversion efficiency and low pollution contingent on the requirement that the original electric power is no produced by the combustion of fossil fuel. (Electric automobiles, William Hamilton. McGraw-Hill Book Co. New York (1980) and Electric Vehical Technology, J. E. Unnewehr and S. A. Nasar, John Wiley and Sons. New York (1982). The well known difficulties associated with adequate energy supply (batteries and fuel cells) for automobiles have greatly limited the use of electric vehicles and have stimulated inventions of what we shall refer to as quasi-hybrid power trains in which conventional engines power an electric generator which in turn provides electric power to an electric motor, charges a battery or both.
In these inventions some power efficiency and pollution control is achieved by operating the internal combustion engine under strict limits of speed and the like, and additional power requirements are provided by the electric storage battery. Unfortunately the watthour efficiency of most types of batteries is relatively low (in the 70% to 85% range). For example the watthour efficiency of lead-acid batteries from full charge to discharge is only about 75% to 80%, although these values may be somewhat higher under cyclic duty. (Mark's Standard Handbook for Mechanical Engineers, Eight Edition, Mc-Graw-Hill Book Co.) This efficiency limitation, as well as the additional weight, cost, inconvenience and the complications of utilizing essentially two separate, but linked power units has limited the use of these quasi-hybrid systems for automotive use. (Electric and Hybrid Vehicles (Energy Technology Review #44), Edited by M. J. Collie, Noyes Data Corporation, Park Ridge, N.J. 07656 (1979)).
Considerable effort has also been expended in the development of Stirling engines in which linear motion pistons transfer power directly into a linear electric motor/generator unit (E. H. Cook-Yarborough et al Proc. I.E.E., Vol. 121. No. 7, July 1974, p.749; George R. Dochat, SAE Technical Paper, No. 810457, International Congress and Exposition, Detroit Mich. Feb 1981; Machine Design Sept. 11, 1986 p.48).
These designs demonstrate the technical feasibility of linear motor/generators for the conversion of thermal to electric power. However they are limited to operating at a constant resonant frequency with constant power output. In addition the energy efficiency of Stirling engines is inherently lower than that of internal combustion engines where the effectively higher combustion temperature determines a higher Carnot efficiency. The Jarret proposal which overcomes the latter disadvantage is still subject to the former (Jan. P. Norbye, Autocar 22 Mar. 1980 P.47).
The above and similar proposals such as The Stelzer motor (Science and Mechanics Nov.-Dec. 1983) all lack a fundamental ingredient which is necessary to provide the versatility required for various practical applications and to allow an optimization of desired characteristics. That ingredient is precise control of the engine's operating parameters.
It is an object of this invention to create a thermo-electro-mechanical engine (or operating in reverse, a pump or compressor, such as utilized in air conditioning and refrigerator units) which forms the basis for numerous improvements in efficiency, pollution control, reliability, versatility, cost effectiveness in operation etc.
It is a second object of this invention to create a thermo-electro-mechanical engine which is easily amenable to comprehensive computer control.
It is an object of this invention to create a thermo-electro-mechanical engine of extreme mechanical simplicity with essentially only one moving part per cylinder associated with the power train (apart from electric drive motor(s) for mobile use) and therefore to provide in optimal manner for improved mechanical reliability, decreased frictional losses, decreased cooling requirements, decreased cost of production and operation, modular installation, and most of all for adaptability to comprehensive computer control (which can only be easily achieved when the mechanical system is so simple that jerk and backlash are negligibly small and therefore do not interfere with the flow of information from and to the computer) and therefore satisfy the second stated object of this invention.
It is an object of this invention to create a thermo-electro-mechanical engine of sufficient mechanical simplicity and reproductibility of operation as to encourage and expedite research into thermodynamic and chemical processes occurring in the cylinder and into the effects of combustion chamber design and operation, the effects of various fuels and the effects of various ignition and valving systems on those processes, and to harness presently available materials and technology in an optimal manner and to provide impetus for the development of new technology and advanced materials to accomplish the first stated object to the highest possible degree.
It is an object of this invention to create a thermo-electro-mechanical engine which may function (i) as an Otto-cycle engine (or "gasoline engine") (ii) as a Diesel engine, (iii) as a Stirling engine, (iv) as a Rankine engine, (v) as any other such engine (which may or may not incorporate some or all of the characteristics of one or more of the above), and to function in all the various possible configurations of the above engines such as four cylinder or six cylinder configurations, and to function in the various modes of operation of these engines such as the 2 cycle or 4-cycle operation etc. and to function as air-cooled, water cooled etc. engines.
It is an object of this invention to create a thermo-electro-mechanical engine which can be used as a stationary engine (i.e. primarily for the generation of electric power or to power a hydraulic pump or the like, or which can be used in mobile applications (i.e. to power automobiles, ships, airplanes, and the like).